I was really struggling trying to fit some parts which I made on my different printers. Have a flavour of mk3/mk4 and Bambu. In an effort to help me out to figure out on which access I had the problem with the accuracy I designed the following.

The Circle ( Z ), Polygon (X) and Triangle (Y) help to ensure the alignment is correct when printing on different printers. The Inner Cube should fit snugly in the Outer cube in every possible orientation. If it does then X,Y and Z are within the tolerances.

I can create multiple versions upon request if needed. These are ( OuterCube ) 50x50x50mm with a wall diameter of 3x0.42mm and wall spacing (tolerance) between OuterCube and InnterCube is 0.20 mm.

The Inner Cube should fit snugly within the Outer Cube in either the X or Y orientation.